About gentzen

Background At the end of 2016, I decided to focus on working through an introductory textbook in quantum mechanics, instead of trying to make progress on my paper(s) to be published. I finished that textbook, which taught me things like … Continue reading →

The previous two posts used the sequent calculus with a subset interpretation: We work with sequents , and interpret the propositions (and ) as subsets of some universe set . We interpret the sequent itself as . While writing the … Continue reading →

In the last post, consideration related to partial functions lead us to present a logic without truth and implication, using the binary minus operation as a dual of implication and substitute for unary negation. But logic without implication and equivalence … Continue reading →

Pi is wrong! But so what? It is neither new, nor complicated enough to count as real math! And suggestions that or might be even better show that it not clear-cut either. I recently invested sufficient energy into some logical questions to … Continue reading →

The end of my last blog post (about isomorphism testing of reversible deterministic finite automata) explained how category theory gave me the idea that the simplified variant of my question about permutation group isomorphism should be easy to solve: The idea to consider … Continue reading →

A deterministic finite automaton (DFA) is a 5-tuple, , consisting of a finite set of states a finite set of input symbols a (partial) transition function an initial state a set of accept states An isomorphism between two DFAs and … Continue reading →

"A good stock of examples, as large as possible, is indispensable for a thorough understanding of any concept, and when I want to learn something new, I make it my first job to build one." - Paul Halmos